JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id='code' cols='50' rows='10'></textarea>
<textarea id='codeblock' cols='50' rows='10'></textarea>

JavaScript

$('#code').on('keyup',function() {
  var code=$(this).val().replace(/(( {4}|\t)(.*?(\n|$)))+/g, function (m) {
    return "<code>" + m.replace(/(^|\n)( {4}|\t)/g,'$1') + "</code>";
  });
  $('#codeblock').val(code);
});